Rolling oils



United States Patent 3,429,815 ROLLING OILS Herbert J. Drake, Nazareth, Pa., assignor to Bethlehem Steel Corporation, a corporation of Delaware No Drawing. Filed Oct. 8, 1965, Ser. No. 494,232 U.S. Cl. 252-495 6 Claims Int. Cl. 'C10m 1/06, 1/24 This invention relates to lubrication of steel strip during cold rolling operations, and more particularly to lubrication of thin gages of strip.

In the cold rolling of steel strip to be used for what is known as double-reduced, or thin tinplate, numerous lubrieating problems develop due to the extreme thinness of the strip being reduced. Thin tinplate has a thickness in the neighborhood of 0.006 inch and, generally, it is reduced to this gage from a gage of about 0.010 inch. The 0.010 inch gage material is obtained by reduction on a 4-high tandem cold reducing mill, and leaves this mill in an extremely hard condition. The 0.010 inch strip is given an anneal before reduction to the finished gage of approximately 0.006 inch. In the annealed condition, the strip requires a control of rolling lubricant not encountered in normal cold rolling. This requirement for control of lubricant is especially true for thin-gaged strip which is to be used subsequently as a base material for an electrolytic tinning operation. In cases where the base steel has been improperly lubricated during rolling, the electrotinned product may have poor or non-uniform reflectivity, generally caused by mottling of the base steel.

In the rolling of the light gages of steel strip, deformities may be caused by localized pockets of heavy lubricant. The lubricant in these pockets can deform the strip surface by hydraulic pressure and produce the phenomenon known as mottling. Mottling is apparent as an uneven appearance, or reflectivity, of the strip surface. Where there are small deformities or depressions caused by pockets of heavy lubricant, the appearance is dull or grayish. This dull, non-reflective surface is caused by the rearrangement of metal crystals during the cold rolling operation. The contrast between the dull patches and adjacent burnished areas gives the strip the mottled appearance. This mottled apperance can still be perceived after electrotinning.

Mottling is not ordinarily encountered in conventional tandem mill rolling because the strip has become work hardened by its passage through the preceding stands. The necessarily severe environment existing in the last several stands, thins out even the heaviest rolling oils sufiiciently so that uniform metal to metal contact is obtained, and mottling does not occur. Furthermore, conventional tinplate receives a skin passing, or temper mill rolling, after annealing, which results in a uniformly smooth strip surface.

Prior practice for rolling thin tinplate has consisted mainly in using either a water dispersion of a fatty oil such as palm oil, or a water dispersion of fatty oil and an oil of the type referred to as soluble mineral oil Neither of the above-mentioned combinations has been wholly effective in producing a satisfactory light steel strip for use as a base metal for thin tinplate.

It is a principal object of this invention to provide a lubricant which will eliminate mottling defects of the rolled steel surface.

Another object is to supply a lubricant to the strip which will disperse readily, yet plate the rolls and strip instantly with a lubricant film which is not easily removed by cooling water sprays.

A further object is to provide a lubricant which permits controlled metal to metal contact between roll and strip surfaces.

3,429,815 Patented Feb. 25, 1969 With the foregoing objects in mind, I have developed a low cost lubricant which overcomes the deficiencies observed with prior rolling oils.

Broadly, the invention comprises applying to the steel strip surfaces, prior to entry into the roll bite, a temporary oil-water dispersion of controlled amounts of fatty oil and a low-viscosity mineral oil. The mineral oil should not be of the class known as soluble oil.

The fatty oil component is used to provide the necessary lubricity or oiliness characteristics to the composition. However, the composition differs from rolling oils used for conventional tinplate on multi-stand tandem mills Where the strip has become work-hardened by the preceding stands. The lubricant generally used in producing conventional tinplate is composed of substantially all fatty oil, such as palm oil. I have found that an ideal rolling oil for reducing annealed strip in the doublereducing operation should have a low viscosity to prevent strip mottling. A suitable low viscosity is achieved by incorporation of the fatty oil with a major propotrion of a low viscosity mineral oil. Under the conditions of double reducing an annealed strip, this combination of fatty and mineral oils provides adequate lubrication, while permitting sufficient metal to metal contact between rolls and strip to produce a bright, burnished strip surface. Such a surface will be bright after electrotinning, even with light coating weights.

The type of fatty oil which has been found to produce the most satisfactory results in my invention is that which contains a preponderance of fatty acids, or glycerides of fatty acids, having 16 to 18 carbon atoms in the acid chain, including palmitic, stearic, oleic and linoleic. An oil of this character is palm oil, which has long been used as the sole oil ingredients in lubricants used for rolling conventional tinplate on a tandem mill. Various palm oil substitute rolling oils, with compositions quite similar to that of palm oil, are also suitable as the fatty oil component.

While the oils just referred to are preferred, as the fatty oil component, many other fatty oils can be used, including, by way of example, corn, cottonseed, peanut, poppyseed, saffiower seed, sunflower seed, soybean, and various other natural oils such as tallows and greases, provided there is at least 7% free fatty acid present in, or added to, the oil. Usable oils comprise those in which the 16 to 18 carbon atom fatty acids represent at least of the total fatty acid content, including free fatty acid and/or fatty acid triglycerides.

In place of a fatty oil, as just described, i.e. one containing fatty acids and triglycerides of fatty acids, a quantity of free fatty acid may be used. Fatty oils which have been hardened or partially hardened by bydrogenation may likewise be used.

For best performance, those fatty oils known to be non-drying or semi-drying should be used. Drying oils such as tung or linseed, if used in any appreciable quantity, are unsatisfactory, as they tend to polymerize into substances having very little lubricating value.

Low viscosity petroleum oils suitable for this invention include those non-soluble, or non-solubilized oils which have a viscosity ranging between 35 and 75 seconds at 100 F. Saybolt Standard Universal (SSU). By the term non-soluble oil, I mean to distinguish from the well known soluble oils which contain large amounts of soap or other emulsifiers to cause the formation of a tight, or stable, emulsion upon addition to water.

It is not necessary that virgin oils be used. Oils such as palm oil or palm oil substitutes, for example, which have been used on a S-Stand tandem mill as rolling lubricant for conventional tinplate, can ibe reclaimed, if suitable reclaiming facilities are available for removing extraneous material therefrom, and this reclaimed material used in the composition of this invention.

The oils may be mixed in the volume range of from 20% to 60% fatty oil and from 80% to 40% petroleum oil. The oil mixture is mixed subsequently with water in a volume range of from 5% to 30% oil, the most desirable amount of oil within this range depending on whether one or two stands are to be used for the rolling operation. If most of the strip reduction is to be taken on one stand, between 12% and 30% of oil will be needed in the wateroil mixture, while about 5% to 14% of oil may be required when reduction is spread over several stands.

The water-oil mixture should be applied to the work rolls and the strip at a temperature ranging preferably between about 100 F. and 170 F.

EXAMPLE I Lubricant was prepared by mixing 15 gallons of reclaimed synthetic palm oil substitute, 15 gallons of light petroleum oil and 90 gallons of hot water in a 150 gallon capacity tank. The mixture was agitated with a slow-speed stirrer for about 5 minutes, the temperature of the mixture being maintained at about 155 F. The reclaimed synthetic palm oil has a saponification value of 160 and a free fatty acid content of Of the fatty acid components present, including free fatty acid and combined forms (triglycerides), approximately 97% had a chain length of 16 to 18 carbon atoms. The petroleum oil had an SSU viscosity of 50 seconds at 100 F.

Rolling of the strip was performed on a four-high, single stand mill' having 18% inch diameter by 42 inch long work rolls. The meta-stable, or non-permanent, dispersion of oils in water was applied to the work rolls, and to the incoming steel strip at a point about four feet from the bite of the rolls. On this particular run, the strip comprised two 6-ton coils of annealed steel strip, the strip being 32 inches Wide by 0.0099 inch thick. The strip was reduced to a thickness of 0.0065 inch in one pass at a rate of 1700 ft. per minute. The strip was later electrotinned, and it exhibited excellent brightness and shape (flatness) properties both before and after tinning.

As the complete reduction in this example was made in one pass on a l-stand mill, the fatty oil and petroleum oil were mixed in a 1:1 ratio, while the oil mixture comprised of the oil-water dispersion.

EXAMPLE II In this run, reclaimed synthetic palm oil and petroleum oil were mixed in the ratio of to respectively. Both oils had the same physical characteristics as those used in Example I. The oils were fed to a 1200 gallon tank along with hot water of a volume equal to three times that of the combined oils, producing a mixture of 25% oil concentration. The oils were dispersed in the water as a meta-stable dispersion at a temperature of about 150 F. by means of a slow speed agitator.

In this example a total of six coils of annealed strip having a width of 35.5 inches and a thickness of 0.0099 inch, with each coil weighing from six to seven tons, were rolled on a 2-stand, 4-high tandem mill. Both stands had 24 inch diameter by 48 inch work rolls. The speed of the strip at stand No. 2 was approximately 2500 ft. per minute. Screwdown pressure on stand No. 2 rolls was approximately 770 tons.

The oil water dispersion was pumped continuously to the mill via a loop, .with any oil in excess of mill demand being returned to the tank. The dispersion was applied by spraying the work rolls of stand No. 2 and the strip just prior to entry of the rolls of stand No. 2. Stand No. 1 was operated in a dry condition, with most of the reduction occurring at stand No. 2 When the work load is divided more equally between two roll stands, the amount of oil in the oil-water dispersion can be considerably lower than in the case where only one roll stand is used.

The strip in each of the six coils rolled was bright and 4 fiat throughout, both before and after subsequent electrotinning.

EXAMPLE III A mixture of one part of reclaimed synthetic palm oil and two parts of petroleum oil was fed to a 1200 gallon mixing tank along with 22 parts of hot water to form a dispersion in which the combined oil represented 12%. Both oils had the same physical characteristics as those used in Examples 1 and H. The lubricant mixture was maintained as a meta-stable dispersion by means of a slow speed agitator, with the temperature being maintained at approximately 150 F. The mill used in this example was the same as that described for Example H. The dispersion was used once and discarded.

Two coils of annealed strip 35.5 inches wide and 0.0099 inch thick were reduced to 0.0085 inch in stand No. 1, and then to 0.0060 inch in stand No. 2 at a rate of 3000 ft. per minute. The screwdown pressures for stands No. 1 and No. 2 were approximately 550 and 660 tons respectively.

The finished strip 'was bright and flat both before and after subsequent electrotinning.

In all examples in this specification and in the appended claims, all ratios, parts or percentages relative to lubricant components refer to volume.

Generally, no surface active agents are needed for the lubricant. However, if the mixing tank is located at a considerable distance from the point at which the lubricant is applied to the rolling operation, agitation facilities are inadequate, water quality makes dispersion diflicult, or the oil-water dispersion is recirculated, a nominal amount of surface active agent may be incorporated in the lubricant mixture. When it is considered desirable to use a surfactant, the amount may vary widelyfrom as low as 0.10% up to 3% based on oil volumedepending on the nature and activity of the surfactant, Also, if the lubricant is used as a combination lubricant and coolant, a surfactant may be used.

The surface active agents which may be used in conjunction with the lubricant dispersion of this invention may include those classed as cationic, non-ionic or anionic, and may be used singly or in combination with other agents. As the activity of surface active agents varies widely in different media, certain agents are much to be preferred over others. Among those agents which give satisfactory results with this invention are the following:

Alkaterge-T (Commercial Solvents Corp.)-substi tuted oxazoline.

Igepal CO-530 (Antara Chemicals)-nonyl phenoxy polyoxyethylene ethanol.

Span 8O (Atlas Chemical Industries, Inc.)-sorbitan monooleate.

Tween (Atlas Chemical Industries, Inc.)polyoxyethylene sorbitan trioleate.

While this invention has particular applicability to the rolling of thin annealed steel strip prior to electrotinning, it is applicable to the rolling of any light gage steel strip material including rolling of gages up to 0.060 inch in a conventional cold rolling operation, where flatness and uniform brightness of the finished product are essential. Furthermore, the advantages of the invention are also obtained when it is used in the rolling of the strip after electrotinning, whether or not the strip is to be further coated after rolling.

The particular combination of an oil in water dispersion of this invention provides for the dilution of fatty oils with a large amount of light petroleum oil to lower the oil viscosity to a degree where localized hydraulic deformation, and mottling therefrom, do not occur. The oil deposition is extremely fast and complete, resisting removal by water cooling sprays, and thus permits both low mill loads and extremely good warm-up characteristics following roll changes.

The term fatty oil, as used in the appended claims, in-

cludes those fatty components -known to be non-drying or semi-drying fats or fatty oils, fatty oils of this nature which have been hardened, or partially hardened, by hydrogenation, and compositions which are substantially 100% free fatty acid.

I claim:

1. In the rolling of light gage steel strip the method of lubricating which comprises applying to the strip at a point prior to the work rolls an aqueous dispersion of from 5% to 30% of an oil mixture wherein said oil mixture contains (A) from 40% to 80% of a non-soluble mineral oil having a viscosity between 35 SSU and 75 SSU at 100 F., and

(B) from 60% to 20% of a member of the group consisting of (a) fatty acid in which a major portion represents fatty acid chain lengths of 16 to 18 carbon atoms,

(b) a fatty oil in which a major portion of the total free and combined fatty acid content represents fatty acid chain lengths of 16 to 18 carbon atoms and which includes at least 7% free fatty acid, and

(0) mixtures thereof.

2. A method according to claim 1 wherein at least 80% of the fatty acid (a) and at least 80% of the total free and combined fatty acid content of the fatty oil (b) represents fatty acid chain lengths of 16 to 18 carbon atoms.

3. A method according to claim 2 wherein the strip has a thickness of approximately 0.006 inch to 0.0065 inch.

4. A method according to claim 2 wherein the aqueous dispersion is applied to the strip at a temperature between about 100 F. and 170 F.

5. A composition for the rolling of light gage steel strip which is to be coated subsequently with tin which comprises an oil containing (A) from to 80% of a non-soluble mineral oil having a viscosity between 35 SSU and SSU at 100 F., and

(B) from 60% to 20% of a member of the group consisting of (a) fatty acid in which a major portion represents fatty acid chain lengths of 16 to 18 carbon atoms,

(b) a fatty oil in which a major portion of the total free and combined fatty acid content represents fatty acid chain lengths of 1 6 to 18 carbon atoms and which includes at least 7% free fatty acid, and

(c) mixtures thereof.

6. A composition according to claim 5 wherein at least of the fatty acid (a) and at least 80% of the total free and combined fatty acid content of the fatty oil (b) represents fatty acid chain lengths of 16 to 18 carbon atoms.

References Cited UNITED STATES PATENTS 2,303,142 11/1942 Spangler 22549.5 2,3 77,106 5/ 1945 'Reswick 25 25 6 2,425,174 8/ 1947 Carmichael 25 249.5 2,617,769 11/1952 Nichols 25249.5 2,896,486 7/ 1959 Donnelly 25 2--49.5 3,031,749 5/1962 Adams 252-495 3,117,929 1/1964 McCoy 25249.5 3 ,25 2,907 5/ 1966 Kharouf 25 2-49.5

DANIEL E. WYMAN, Primary Examiner.

CARL F. DEES, Assistant Examiner.

US. Cl. X.R. 252-56 

1. IN THE ROLLING OF LIGHT GAGE STEEL STRIP THE METHOD OF LUBRICATING WHICH COMPRISES APPLYING TO THE STRIP AT A POINT PRIOR TO THE WORK ROLLS AN AQUEOUS DISPERSION OF FROM 5% TO 30% OF AN OIL MIXTURE WHEREIN SAID OIL MIXTURE CONTAINS (A) FROM 40% TO 80% OF A NON-SOLUBLE MINERAL OIL HAVING A VISCOSITY BETWEEN 35 SSU AND 75 SSU AT 100*F., AND (B) FROM 60% TO 20% OF A MEMBER OF THE GROUP CONSISTING OF (A) FATTY ACID IN WHICH A MAJOR PORTION REPRESENTS FATTY ACID CHAIN LENGTHS OF 16 TO 18 CARBON ATOMS, (B) A FATTY OIL IN WHICH A MAJOR PORTION OF THE TOTAL FREE AND COMBINED FATTY ACID CONTENT REPRESENTS FATTY ACID CHAIN LENGTHS OF 16 TO 18 CARBON ATOMS AND WHICH INCLUDES AT LEAST 7% FREE FATTY ACID, AND (C) MIXTURES THEREOF. 